Oscillator



Jan. 15, 1957 J. A. DOREMUS 2,777,950

OSCILLATOR Filed March 25, 1953 Fig. 2

Impedance INVENTOR. John A. Doremus United States Patent cc Patented Jan. 15, 1957 oscillations. A point contact transistor of the PNP type, having a current gain of more than one may be used. The frequency of the oscillations is controlled by an ,950 electro-me'chanical vibrating reedstructure which has an OSCILLATOR 5 impedance curve having sharp peaks so that accurate frequency control is provided. In one embodiment the John A. Dorcmus, Chicago, 111., assignor to Motorola, electro-mechanical unit is connected to the base electrode Inc., Chicago, 111., a corporation of Illinois of the transistor to provide oscillations at the resonance point (maximum impedance). In a second embodiment Apphcahon March 1953 Sena! No'343963 the electromechanical device is connected between the 4 Claims. (Cl. 250-36) emitter and collector electrodes '80 that oscillations are provided at the anti-resonance point (minimum impedance).

Referring now to the drawings, in Fig. 1 there is illus- This invention relates generally to accurately controlled trated an oscillator circuit including a transistor 10 of the" oscillators, and more particularly to alow frequency oscilpoint contact type, or any type having a current gain lator system which includes a transistor unit and a vibratgreater than one. The transistor 10 includes a base" ing reed electro-mechanical structure for controlling the electrode 11, an emitter electrode 12 and a collector elec-- frequency thereof. trode 13. The base electrode 11 is connected to ground Accurately controlled low frequency oscillators are gh t l 5 f an le tro-m chanical device 14.- required in various different applications such as selective The device 14 includes a reed structure 16 rigidly mounted; signalling systems and also as tone sources for electrical in a support 17, and having the ends thereof positioned musical instruments. Electro-mechanical structures inj cent ag etic poles 18 and 19. The reed 16 is cluding reeds mounted in magnetic fields have been used adapted to vibrate with respect to the coil 15 and the for accurately controlling the frequency of such oscilpoles 18 and 19, and affects the resonantdmpedance of lators. In such oscillators one or more tubes have been h Coil The emitter electrode 12 is grounded used to provide the oscillating circuit, and th l t othrough biasing resistor 21 and the collector electrode 13 mechanical device and a plurality of other coupling comis cofllleeted to a Source Of negative Potential 22 by ponents are required to form a relatively complicated and sister 23. Oscillations may be derived from the circuit expensive unit. Further such circuits require relatively h gh c ndenser 24 which is connected to the collector large operating voltages which must be maintained within electrode 13 or from a lead 20 Connected to the p of reasonable limits to hold the oscillator frequency stable. the coil of the c nical unit.

It is therefore an object of the present invention to Considering now the Operation of the circuit of provide an improved oscillator circuit of extremely simple Oscillations will take Place in the Circuit at the construction. quency at which the regenerative action is maximum.

A further bject of this invention is to provid a law This occurs when the impedance Of the circuit Of the frequency transistor oscillator circuit wherein the frebase electrode 11 is maximum The impedance of the quency is very accurately maintained, electro-mechanical unit 14 is illustrated by the curve of A feature of this invention is the provision of a trana- 2 and this impedance a y fp maximum sistor oscillator circuit including a vibrating reed electro- 49 Phlht at the frequency Thls frequency 15 l shghtly mechanical structure for controlling the frequency therelower than the natural freqhehcy of Vibrahon 0f the of. This oscillator requires a minimum of components reed The frequency F1 calledfhe rescue-hf and willoperate atavery low voltage quency of the electromechanical device. Accordingly,

Another f t f this invention is the Provision of the oscillator of Fig. 1 Will oscillate at the frequency F1 a low frequency oscillator including a point contact tran- Winch h Impedance of the electro-mechanical desistor having an electro-mechanical vibrating structure Vice 1s maxlmum- :Ihls freqhhhcy be accurately connected in the circuit of the base electrode thereof} trolled-P3 colitmnmg the dlmenslons of the electro' This circuit will oscillate at the resonant frequency of mechamcal f the electro-mechanical structure at which the impedance Reference i now made to 3 whlch luhstrates the is maximum 5o physical details of an electromechanical device for use A further feature of this invention is the provision of m the osclnator m amrdanqe Yvlth h mvehtiom This a transistor oscillator circuit including an electro-mechanstrhture may be gfinerauy h to that hsclosed and ical vibrating structure coupling the emitter and collector claimed mpehdmg apphcahon of holzmger et electrodes to provide oscillations at the anti-resonant or Serial i h 1950 enmled low impedance point of the characteristic curve of tha b5 tro-Mechanical Device, and assigned to the same assignee electro mechanical structura as the present invention. In this structure the same refer- Further objects, features and the attending advantages h humerals are applied as The base and of the invention will be apparent from a consideration of V1brahng re?d 16 are made of maghehzahle mammal and the following description when taken in connection with the h secured to i baseh reed and base the accompanying drawings in which. are positioned in a sheet metal inner housing 25 of rectan- Fig. l is a circuit diagram of an oscillator circuit in gula? chhfiguratloh wlth the reed extehhhg along the accordance with theinvention; longitudinal axis of the housing. The housing 25 also Fig 2 is the impgdance frequency characteristic curve includes a permanent magnet structure including the north of h electfo-mechanical ib ti Structure; magnetic pole 18 positioned on one side of the free end Fig. 3 shows the physical construction of an electroof the reed, and the south magnetic pole 19 positioned mechanical unit which may be used in the circuit of on the other side. Surrounding the reed 16 and between Fig. 1; and the base 17 and the poles 18 and 19 is the coil 15. This Fig. 4 illustrates a second circuit embodiment in accoil is connected to plug-in contact pins 26 and 27 on the cordance with the invention. mounting base 28. An outer housing 29 is secured to the In practicing the invention there is provided an oscillator circuit wherein a transistor is provided for sustaining mounting base, with the inner housing 25 being supported therein by springs 30 and 31. The springs 30 may also.

provide electrical connections between the coil 15 and the contact'pins'26'and 27'."

current signal is applied to coil 15 caus e s 't't'o reach a maximum val neat -9x1 F as i l s rs e ta l e-Z1 A et i ly ator. fjig, 1 wil there for ex osc l tjtta ba s at ae et tti v a :;Fwdhasl ismY dnlim se lsstatsl atm 3 v. to h em te enc -Q th sh t eel t esh ise ,t is am be i he a e tsen al, sh t qtt as do" 1 a F es ilhetrs sstia ia s -t T em-mech n l, d vise ialu t99 1- $iw ht cp ted-is se ie w h dsnssafl be ween 411?, emit e -3 so le tgt el ctrode e m ne ic.t dt'iyibt t e hiath .sg lfti a d w h re pect masneticip es 46 id? as as b en tu lyex l in de T he si uit Q F a- 4 i os llate w enit imn dan a in the feedback circuit is a minimum. shown by the ra t is iaq yepf H st; 2 the e ect veiimpedascect izo of h a s -m hani al n iis at m n mum t the ireque y. 2 wh ch is a s ght vl igher. r que cy h n ..I, t inequ ty n h c i he natural fr quency oi v z. t tion of the reed, he, .frequencyfll'iz is called the; anti-v resonant pointyof the. electromechanicalhdevice The, circuit ,of Fig 4 will,-,therefore, oscillate at a slightly higherfrequenej than the circuit of Fig.1 when; the. same electromechanical.device ,is used. Theroutputhof the,=.., circuitot Fig; 4 may b eriv d fromci er th mi tenas or collectortelectrodes..Jn Fig. 4, theoutputof the b os-ii, cillatormay. be derivedfrom thecollector electrode .3 9 ,t t throughcondenser 48. v

It isithereforenseen .fronrthe above thatithere ,is P1101, vidediin accordance withtheiinventionan improved .os- 50 cillator circuit which is of extremely simplevconstruction. Thest'ransistor unit which sustains -,oscillationsi requires a.- minimum Lot coupling components and operates ,from a veryllow potential to. thereby conserve .power..-Thepre-. r. cisioni-of the electromechariicaldevicev will .depend upon .55 the .accuracy of the frequency. required, J and .by careful; constructionhighly accurate frequencylcontrolfin the low t frequencytrange can be provided. The, coupling of this devicelmaybe very simply accomplishedso thatrthe. over-.. 7, all circuitrequiresa very few components and is. therefore (30 relatively inexpensive.

Although certain embodiments of the invention have, ,i been disclosedwhich are illustrative thereoflit is obvious, thatr'various changes and modifications can be made in the invention within the intended scope .of the inventionhti as definediin the appended -i,

I la m a v 1. An oscillator circuit whichoperatcs at a predator; nsdire asyn lwl e in biQEE- PP wa st-te m? the P h i, andcol- T0 quency, meansconnecting said winding between said base electrode 'of said transistor'and a reference potential, and circuit means connected to said emitter and collector electrodes of said transistor for biasing the same, said winding providing feedback for sustaining oscillations in the circuit and providing a direct current path from said base electrode to said reference wpotential, said electromechanical device being the s ole frequency selective means in the OsciHator ci'rcuit-and providing feedback ts tei nene ci l tisa an tsa sa d: r deter in ttea frequenby. t l. t.

2. A low-frequency oscillator circuit including in combination, a transistor having an input electrode, an output electrode and a comnign electrodeg aninput circuit connected between said in'putelect rodeanda point of reference potential and including biasing means for said input electrode; an output circuit connected between said output fitmlsa d-sa Pa t i ts s e eqpo at a i di f. 'nsiash fl t s 9 $a dtc aa' t a sl rl l ire-a cesse de vice havin g amagnetizable reed d. for vibrat ongand'having.ipearis eluding an induc winding 'for' establishing a magneticfield forfyibratin ding exhibiting ausharp maximum unpedan eak re ti ufency relateti to the when shest P; la .a ais tsat se dl ans con ctives: said win ingubetw een saicl common electrodeand said pointj of iif c e; pote ntialYtoprovide a direct current P nthe s? tw en am s ta iuen ts ive v tw k for feed ing energy tromsaidputputcircmt cuit of appropriate phase to slustaiiroscil; Q

. el cal l vi e be n -mar e s!- ans in the. oscillatorcircait whereb in d at the rgeqqeh yer saidmairim t j i i i i -l; I I

qi n' lms illatc r i tg n t ins n we e.

es tb'iltav aafi t i ds ai ls ttsd sand; a co onele trode cooperating'therewith, a first circuit connected between said first electrode and a point of e en e men al-a d in d n b n m man i games. e nd! r' u fso mc t dib s n sa d secon electrode and said poin't of'reierence: potential'and including biasing neans giort said second electrode,,an H r ms heai a device t w e, a m enet z' ble. re d a; mounted for vibr on and'asingle inductive winding for establi sh in la magnetic field for said reed, with said it winding exhibiting a she "maximurnirnpedancepealt at a p determine t l eilaxi la d i n al-i quency f i n. 9f l d se ia lm a sflw n st n i saidw mding bet een said common electrode and said i of reference potential, said winding providing e t cur e th rom a d s nsl gde-tg Said, itq j f e ns ns' et a sai Qe s t qm shaa s def e being the sole frequency-selective means in the oscillator circuit and feeding energy from .salclsecond circuit to Said'firt sir i ann etitia e P a e a ain O la ns,

esne u sev whereby oscillations are; sustained in said illtitofcircuit at the freq uency dream maXim'tim'irnpe nceipeak of said vvihding; i

41n'lawtrauene "estimator circuit including in combination, a transistor having an emitter electrodefa col lector electrode" and a base electrode, a first circuit conh nected'bet'ween :saidernitter electrode 'anda point of M reference potential and including biasing means for said j emitter electrode, a second "circuit connected between said collector electrode and saidpointof reference potential andincluding biasing means for said collector elec trode; an electromechanical device having a magnetizable reed mounted for vibration and a single inductive winding fores'tablisiiinga magnetic field forisaid reed, with said winding-exhibiting a sharp maximum impedance peak-ata 1 frequency related to the natural frequency of vibration 0i i said reed, and means connecting said winding between said base electrode and midpoint of reference-potential, said winding; providing a direct fcurrent path from v said baser electrode t'b'said "point of reference potential, saidielec tromechanical device being frequency-selective for feeding 2,547,027 Winkler Apr. 3, 1951 energy from said second circuit to said first circuit of 2,692,337 Hanson Oct. 19, 1954 appropriate phase to sustain oscillations and being the sole frequency selective means in the oscillator circuit, QTHER REFEREPICES whereby oscillations are sustained at the frequency of said 5 Transistor Osclllators, RCA Revlew, Endefs, and

maximum impedance peak f id i di Moore, vol. XIII, No. 3, September 1952, pages 369-385. Article: Junction Transistor Equivalents Circuits and References Cited in the file of this patent Vacuum-Tube Analogy, by Giacoletto, pages 1490-1493 UNITED STATES PATENTS of Free. I. R. B, vol. 40, No. 11, for November 1952,

D' 51. 2,396,224 Artzt Mar. 12, 1946 W 

